When transmitting a digital signal via a transmission line, ringing, i.e., a distortion of a waveform of a signal such as overshoot or undershoot may arise on a reception side since a part of signal energy reflects when a signal level is changed. Various techniques for restricting the distortion of the waveform are conventionally proposed. For example, Patent Literature 1 discloses a technique for restricting the ringing by adjusting an impedance only in a predetermined period which does not affect communication while a voltage level in the transmission line is switched between a low level and a high level (See FIGS. 8 to 11).
In fifth embodiment of the Patent Literature 1, an element for restricting the ringing is prepared by a structure such that a N channel MOSFET and a P channel MOSFET are connected in parallel to each other between a high potential signal line and a low potential signal line. The N channel MOSFET is operated by a voltage between a power source having a voltage Vcc and the low potential signal line. The P channel MOSFET is operated by a voltage between the high potential signal line and a ground. Thus, even if an offset is generated in a ground potential at a communication node, at least one of the N channel MOSFET and the P channel MOSFET restricts the ringing.